A lot was said before a single word was spoken.

Hillary Clinton and Donald Trump did not shake hands at the outset of Sunday's presidential debate in St. Louis — a mutually passive-aggressive act so unusual that journalists anticipating a tense evening were still gobsmacked by what they saw. Or didn't see.

Trump and Clinton have been running hard against each other for months, but they managed to exchange pleasantries before the first debate on Sept. 26. Reporters who have covered many heated races in the past expect candidates to at least feign politeness when they meet on the debate stage.

But Sunday's non-shake between Clinton and Trump is just one more thing that experienced political journalists have never seen before.